Bristle setting



June 23, 1953 K. v. HARDMAN ETAL 2,643,157

BRISTLE SETTING Filed Feb. 27, 1952 2 Sheets-Sheet l ms y 1 VENToRs 8 l Hennef/1 'lardmdn,

/l TTURNEY June 23, 1953 K. v. HARDMAN ETAL 2,643,157

BRISTLE SETTING Filed Feb. 27, 1952 2 Sheets-Sheet 2 @van IN V EN TOR Patented June 23, 195.3

BRISTLE SETTING VKenneth V. Hardman, Upper Montclair, and Arthur J. Lang, Cedar Grove, N. J., assignors to H. V. Hardman Company, Inc., a corporation of New Jersey Application February 27, 1952', Serial No. 273,710

l 9 Claims.

The present invention relates to a method of setting bristles in a brush. This application is a continuation in part of our copending application Serial No. 75,856, filed February 11, 1949, now abandoned, covering the same subject matter.

In setting bristles in brushes in an operation of the general type of our method, it has been customary heretofore to assemble the bristles with their butt ends up and within a ferrule, pour bristle setting cement over the butt ends ofthe bristles, allow this cement to flow downward by gravity between the bristles, and then to harden the cement, as by heating.

Difficulties have arisen in this operation. As one example of these, the extent to which the cement flows downward between the bristles is diicult to control and variable. When there are crossed bristles in the assembly or loose spacing of some of the bristles due to other causes, then the cement flows relatively rapidly at that point and gives streamers sometimes referred to as icicles of the cement.

The present invention provides a method that avoids the objections to the usual methods. It provides a method in which the extent of downward seeping of the bristle setting composition between the bristles is restricted to a certain definite zone or floor, with the prevention of the formation of the icicles or like structures referred to above. It provides a finished brush in which the bristles and cementing composition are firmly united and the composite so made is firmly united to the ferrule. Y I

Briefly stated, the invention comprises the improved method herein described. The method includes the assembly ofthe bristles vWithin a ferrule, with the butt ends up, pouring over these butt ends a heat thickenable and then heat hardenable bristle setting composition, and establishing the elevated temperature of thickening of the composition within a narrow zone extending across the ferrule at a predetermined level at approximately a right angle to the direction of extent of the bristles. When the composition reaches this zone, the composition thickens `quickly and forms a noor below which there is no further penetration. The invention comprises establishing this high temperature zone which is to constitute the iioor by means of dielectric heating by high frequency energy.

in the preferred embodiment, the invention comprises also the step of supplying the high frequency energy for heating through the ferrule of the brush, the material of the ferrule preferably being electrically non-conducting.

. 2 In a modification,v the invention includes the step'of deflecting'the high frequency energy as it ,tends 'to spread between the electrodes and the ferrule, socas to confine the area of heating to a more limited zone or band.

In another modification the invention includes efecting the heatingbetween a conducting ferruleconstituting. one electrode and another electrodedisposed in the midzone Within the ferrule. The inventionwill be illustrated in connection with the attached drawingsto which reference is made.

VFig. 3 is asectional view on line 3 3 of Fig. 1,

with electrodes added and shown in broken lines.

. Fig. 4 is a fragmentary enlarged View of a portion of a brush broken away for the purpose of illustration.

Fig. 5 is a sectional view of a modied form of assembly utilizing an inner electrode and a conducting ,ferrula Fig. 6 is a sectional View on line 6 6 of Fig. 5.

Fig. '7 is a rview similar to that of Fig. 4 of a modified form ofthe invention. Fig. 8 is a sectional view on line 8-8 of Fig.` 7. y Fig. 9 is -a sectional View of an assembly used in a modification of the method of manufacturing the brush. Fig. 10 is avmodied form of assembly similar to that vof Fig. 2 with the electrodes positioned .below the ferrule.

Figs. l1 and 12 show a modified form of electrode. Y

The views on the several section lines stated .arein the directions of the arrows. Parts not illustrated specifically are conventional unless otherwise described. y

There are shown a brush with handle IU of conventional type, ferrule4 l2, bristles I4, spacer -strips IB, and fasteners of usual kind suchas rivets I8 extending through the ferrule and material disposedtherewithin. The bristle setting composition 20 lsuitably extends as a cap over the butt ends lofthe bristles as shown in the sectional views. Thisv bristle setting composition also extends downwardly between the bristles to the setting zone illustrated at 22. The capis shown at 20.

There are shown the electrodes 24 and 25 used in supplying energy during manufacture, with leads 28 and 30 Yconnecting the electrodes to a conventional high frequency energy machine (not shown). During the high frequency heating operation, these electrodes are brought close to the outside of the ferrule.

In the modification shown in Figs. 5 and 6 a conducting strip 32 is joined, for the step of establishing the oor 22, at one end to an inner electrode 34 terminating at points about ,equidistant from the ferrule in all directions. The ferrule 36 in this case is a conductor of electricity. The strip 32 is joined to one pole of the high frequency energy machine by lead 38 and the ferrule is connected by lead 40.

Figs. 7 and 8 show a modification ofthe struof ture in which an electrically conductingl st rip 42 of sheet metal or the like is disposed within the ferrule as shown, so as to shield a part of the butt portions of the bristlesffrom thehigh fire; quency energy.

In Fig. 9 there is shown another modification in which high frequency energy deilectors 44 are disposed'adjacent to theferrule and to the sides of the electrodes 24 and 26 so as to narrow the zone of heating by the high frequency energy, as shown by the broken lines in the figure.

In Figs. 11 and 12 we show a modified form of electrode which is advantageous for producing extremely uniform heating conditions throughout the narrow zone. or fioor in the ferrule. `As shown electrodes 24 and 26 (a) are fiat and made to extend slightly out beyond the ends. of bristle mass 4.6 anda pair of blocks. of non-conducting material 48 such as teflon or the like are interposed between the extended ends of the electrodes. Teflon is also used to coat the inside edges. of the two electrodes with a lm (50) approximately .005 inch thick. These modified electrodes oper ate in the same. Way as those. described in the primary form of ouriinventionand the non-conducting material provides an even distribution ofthe high frequency energy so that there is less tendency to overheat and char the setting composition.'r

' Materialsof construction of. the` various. parts are those that are conventional for. such use unless otherwise. stated.

The bristles may be any. one off-the commercial bristles used in making. paintbr-ushes on the like, as,V forl instance, nylon,'hogbristles-, horsehair, bersi such 'as Tampico, orfcellul'ose triacetate.

It-will` be appreciated that nylon' and triacetate l for this purpose are suitably in theV form of the Vtapered filaments nowmade for paint brush use.

Nylon bristles, although difficult -to set properly by usual means, are set satisfactorily and conveniently-,by our method.

When the method of heating involves the assemblyshoi'ivnin Figs. 2,' 3,' 4, fl, 8 andQth'e ferrule is preferably' noncnductingsince it is? dicult .to achieve the required Vteinper'stufe forlhardening the setting composition ita conducting ferrfule vis positioned betweenl theelectrodes.Y However this d-iicultyis yread-ily solved by. positioning" the electrodes 'justfbelowfthexnetal' fer-rule as "best shown inf Eig'. 10.V In. operation highffrequency energy passes between the individual electrodes to produce dielectric heating V'of the bristles'.` and setting composition.'within'the ferrule;-D This energy' establishes the heatedL zoneuoroorwhich prevents further penetration 4ofthe heatsensit'iv'e cement.

Examples of ferrules that are non-conducting and are used to. advantage areY nylon in molded form and shaped as shown, aphenolaldehyde irnpregnated and laminated clothrfpapr sheet, plastic., Jrearl.v silica compound. (siliconen `and 4 rubber and acrylonitrile plastic. Such ferrules should be resistant to organic solvents of kind used in paints, varnishes, and lacquers. Metal may also be used for the material of the ferrule if the method oi manufacture is one using the assembly shown in Figs. 5, 6, 10 and l2.

Spacer strips 1,6 may beof wood, plastic, or like electrically non-conducting material. In any case the material selected is in the shape desired for the ferrule, as in one of the oblong 'tubular forms shown. When wood strips are used, the strips' may be predried, to remove excess moisture.

The bristle "setting composition should be one thatv is heat thickenable and then heat hardenable'. 'Examples are the various flowable plastic co'-nposi'tins`o`fl about the consistency of heavy syrup, includ-ing phenolaldehyde condensation proy uct, urea-formaldehyde condensation product," nd a viscous mixture of styrene and polystyrene. In some cases the setting composition has va tendency to. shrink away from the ferrule when it. hardens and this results in a poor bond. Such shrinkage readily be avoided by adding a blowing agent such as diazoaminobenzene, sodium bicarbonate or. ammonium carbonate. to the setting. composition all as described in U. S. PatentNo. 2,496,732, issued to Kenneth V. Hardman on August. 1946.

The high frequency energy machine used for the heating is selected. in accordance with existing knowledge and practice, to give extension of the heating zone completely through the width and thickness of the spacegithin the ferrule, that is, through the. bristle buttsand setting composition therewithin. The high'frequency may be that generated by. a standard machine for use inthe internal heating of plastics.

Wel have used to. advantage a machine giving energy. of frequency. above 30 megacycles a second; With a lower frequency than about. 20 megacycles, heatingv initially is somewhat slower than preferred for the present. purposes.

Theinventionwill.be further .illustrated by the following specific examples. orthey practice ofy it.

Eternia i The butt end soi tapered nylon bristles arel asn Settled w .in @tutelar nylon ferule' i2, 'es illustrated-in l, but with the handle not'yet in position. A` bristle setting composition consisyffi'ng ot a phenol-aldehyde mixture with 8% of setting catalyst, such as phosphorous acid, is applied over the upward or butt ends off'the brisH tl'esginV amount to form about a g, inch layer over the butts. Ellectrodes in the form of copper tubingy of one-fourth inch diameter shaped as shown;` in Fig'. 3- are brought adjacent to the nylon ferrule, on opposite sides thereof, and the high frequency electrical machine attached at its. ter minals to leadsriig: and 3i? is then set in operation.

TheL first effect of the frequency'lieating is moderate warming of the bristle setting corn-- position a-nd increase of its fluidity. As a result, the bristle composition flows downward tothe zone lying approximately directlybetween the electrodes 2id and 263 and adjacent to the lower edge: of the ferrule. The composition, strikes in that zone a high temperatureat least equal to that of the quick thickening of the bristle setting composition, as, forinstance, about -250 the selected temperature being established by prop-er. control of ther energy machine. Here the composition becomes. non-flowable, concentrates as a layer, and. establishes a floor through which additional portions of the composition flowing downward do not penetrate.

rShe effect of the high frequency heating on the bristle setting composition became apparent in about 20 seconds after the current was turned on. Bubbles of steam began to rise in various parte. of the composition and the composition flowed substantial proportion quickly to the level of the very hot floor established by the level of electrodes and 25. The energy supply was then turned down slightly so that boiling of water in the cap 29 practically stopped.

after about 60 seconds of this heating, the floor was well established and the limit to which the setting composition penetrates downwardly between the bristles was established. After about another 30 seconds, the heating by the high frequency energy was discontinued and the assembly so made was then delivered at once and without any substantial cooling to a hot air oven of temperature known to cause a commercially satisfactory rate of nal cure or setting of the phenol-aldehyde condensation product. There the product was fully cured. It was then removed from the oven, cooled, and supplied with handle lil in a usual manner.

Emample 2 In a modification of the above described method, there is used the construction shown in Fig. 5. :fiere a metal ferrule serves as one electrode of the high frequency machine and the metal strip 32 as the lead in from the other pole of the machine to the inner electrode 34, suitably of aluminum metal or the like.

When the setting cement has been cured and the assembly i5 ready to receive the handle I, the strip 32 is severed near the cap 20 and the free end discarded.

Eample 3 The procedure of Example 1 is followed except that deflectors 44 consisting of electrically conducting sheet material such as aluminum, copper or iron are disposed adjacent to and on either side of the two electrodes so as to limit the width of angle through which the energy may arch itself, as it moves to the ferrule and through the materials assembled within the ferrule.

Example 4 The procedure of Example 1 is followed except that a thin band of aluminum foil of thickness 0.005 inch is placed inside the ferrule and outside the bristle butts as shown in Figs. '7 and 8. This narrows the zone of intense heating by screening the area inside the band from the high frequency heating. The band remains in the finished brush. The foil may be copper or iron.

If desired the final curing of the bristle setting composition in a conventional hot air oven as described in Example 1 may be substituted by an additional short heating period with the high frequency energy, the time and temperature of cure being those required to harden the setting composition. rihe supplemental hot air oven is preferred, however, because its use as supplementary heating means releases the high frequency equipment for use on subsequent assemblies in which the floor of bristle setting composition is to be established. If speed of setting is not required, the setting may be effected at temperatures` as low as room temperature. It is necessary, however, that the hot floor 22 be established initially to control the level of penetration.

..6 yThe plastic ferrules fit tightlyi around the bristle setting in the finished article. Such fervrules have a relatively high temperature coeicient of expansion. As a result, they shrink tightly around the setting, particularly when the setting composition has been cured by heating.,

The use of the highfrequency energy heating establishes initially a higher temperature in the bristle setting composition than in the bristles themselves, with the result of giving fluidity and conformance of the cement to the surfaces of the bristles without overheating the bristles. This raising of the setting composition to a tem- `pera-ture"above that of the bristles themselves is particularly pronounced in the presence of a small proportion of water such as found in most of the owable plastic compositions used for bristle setting or generated during the initial stages of the condensation of the resinous materials.

It will be understood that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.

What we claim is:

1. In setting bristles the method which comprises assembling the bristles with the butts up within the ferrule, applying over the butts a bristle setting composition that is owable, heat thickenable, and heat curing, causing the setting composition to penetrate downwardly between the bristles, introducing high frequency energy into the setting composition, in direction generally perpendicular to the length of the bristles and in a narrow zone at the level at which the penetration of the setting composition is to be arrested, the high frequency energy being regulated -to cause an elevated temperature as high t least as the temperature of rapid thickening of the said composition to non-flowable condition and below the temperature of deterioration of the'bristles and the result being thickening of the said composition in the narrow zone to nonlowable condition and the establishment of a oor limiting the depth of penetration of the composition between the bristles.

2. The method described in claim 1, the narrow zone being adjacent to the lower edge of the ferrule and the product made as described being then warmed to and maintained at the temperature of curing of the said composition until the composition is cured.

3. The method described in claim 1, the bristle setting composition being a heat hardenable phenolaldehyde condensation product and the temperature established initially by exposure of the said condensation product to the high frequency energy being higher than the temperature within portions of the bristles adjacent to the said composition.

4. The method described in claim 1, the bristle setting composition containing water and the temperature established initially by exposure of the said condensation product to the high frequency energy being higher than the temperature within portions of the bristles adjacent to the said composition. Y

5. The method described in claim 1 which includes the step of positioning within the mass of bristle butts an electrode which cooperates with the ferrule for introducing high frequency energy into the setting composition.

6. The method described in claim 1 including placing an electrically conducting shield in the path of 4a part but not all of .the .high frequency energy and between the source of said .energy and the bristle ysetting composition .so as to limit lthe Width of the zone subjected to direct heating by the high frequency energy.

7. The vmethod described in .claim 6., the said shield including a band of electrically .conducting metal disposed around `the bristles and at the level of a boundary of the zone to be subjected to heating, so as to increase the temperature gradient at this level and restrict the `width of the said zone of heating.

8. The method described in claim 1 which in ychicles thestep of positioning below the `f errule a pair of oppositely disposed electrodes which c0- operate With each other for introducing high frequency energy into the setting composition.

9. The method described in claim 8 in Which the electrodes are flat and are extended out .beyond the ends of the bristle mass with a pair of blocks of non-conducting material interposed between the extended end portions of the elec- `10 trodes.

I KENNETH V. HARDMAN.

ARTHUR-J. LANG.

No references cited. 

